Thoughts from the intersection of science, pseudoscience, and conflict.

science

The excellent podcast Archaeological Fantasies recently had me on as a guest for a wide ranging discussion on genetics. We covered everything from the genetic prehistory of the Americas to issues surrounding ancestry testing companies. Here’s a link to the episode (apologies for the fact that I kept cutting in and out–apparently our university wireless connection isn’t very good).

Since so much of our discussion focused on haplogroup X2a and models for ancient American prehistory, I decided to break from the normal tradition here at VM and actually re-publish a post to make it easier for people to get answers to any questions they might have. And if you have specific questions about content from the podcast, please feel free to leave them in the comments on this post.

This post was originally published last year to address some questions that Deborah Bolnick and I were getting about our paper “Does Mitochondrial Haplogroup X Indicate Ancient Trans-Atlantic Migration to the Americas? A Critical Re-Evaluation.” I’ve edited it slightly to reflect the fact that the paper itself is now open access, and you should be able to download it here or at my academia.edu page. (I’m actually really shocked at the number of downloads it’s gotten…apparently this is a topic that a lot of people find interesting!).

As soon as my syllabi for the upcoming semester are finished, I will try to write up another post that summarizes recent findings in North American anthropological genetics, and what they mean for our understanding of the initial peopling of the Americas. In the meantime, if you’re interested in ancient DNA I highly recommend you get up to speed on some of the methods by reading this post.

As I’m putting the (hopefully) final touches on a short textbook that I’m writing entitled “Handbook on Science Literacy”, I’ve been thinking a lot about how to recommend a person go about systematically investigating a scientific issue without having any background in it. Sure, you can learn how to read and understand a scientific article, but let’s be honest—far too many people choose instead to do a quick web search and let that settle the question. This practice works okay in some instances, but in others it produces misleading or wrong answers.

I want to share with you my strategies for flunking out of the University of Google.

This is one instance where flunking is a good thing. A graduate of the University of Google chooses to accept only information that supports his or her position, and ignores or dismisses information in conflict with it. A graduate of the University of Google will not be able to answer the question “What kind of evidence would change your mind on this subject?” It’s insidious, because once their opinions are formed in this way, they tend to identify with other people who share those opinions, and any new information that comes their way will either be accepted or rejected on the basis of which position they’ve already taken (the cultural cognition effect)

None of us want to be that kind of person.

Flunking out requires a decent amount of work, and the willingness to accept that you might be wrong about a subject from time to time. You’ll need to become more aware of your own cognitive biases, and have some strategies for overcoming them.

So as a preliminary step down the road to science literacy, I’ve put my thoughts on this together into a guide to learning about a subject in which you have no background. It’s an exercise; please don’t shortcut the process and go to Wikipedia, or you’ll miss the whole point.

Side view of the HERA project facility. The hygiene module, where bathrooms and showers are housed, is in the foreground.

What happens if you put a group of adults together in a confined space and leave them isolated for weeks? Can they get along? Can they work together to productively carry out complex tasks, stay in shape, and conduct scientific research?

This sounds like the premise for a reality show (minus the scientific research part, which sadly doesn’t play well on television). And in a way it is: these adults are filmed every second of the day. But instead of entertainment, this project has one very serious goal: develop strategies for keeping humans healthy, sane, productive, and safe for long duration voyages into space.

The Human Exploration Research Analog (HERA) project is a critical component of NASA’s Flight Analogs Project, which carries out research on different aspects of human long-duration spaceflight. I recently visited NASA to give a talk on genetics to ISS scientists, and was able to tour the HERA facility and talk about the project with its former director, Joe Neigut. Because this isn’t the sort of thing that one gets to access on the regular Johnson Space Center tour, I asked the NASA officials if it would be all right for me to write a blog about my experiences to share with readers, and they kindly agreed, stipulating only a few restrictions on what I was allowed to share in the interests of research integrity. So here’s what I saw and what I learned. Continue reading →

This article is cross-posted from the Social evolution forum where I occasionally write about issues in human evolution.

A new paper out last week in Nature by Sutikna et al. has generated a great deal of excitement, by reporting a revised date range for the diminutive hominin, H. floresiensis, nicknamed the “hobbit” because of its stature (just 3.5 feet for adults). The previous accepted date range for H. floresiensis (95,000-12,000 YBP) implied that humans and hobbits co-existed on Flores for some considerable period of time, prompting fun analogies to the setting of J.R.R Tolkien’s legendarium, Middle-earth, in which humans, hobbits, dwarves, and other races co-existed and interacted. (I actually love this comparison, because it really resonates with my students and makes teaching human evolution easier.)

The original dates for H. floresiensis were based on the (then reasonable) assumption that the depositional sequence in one part of the cave was representative of other parts of the cave. But caves are very active geological systems, and it often turns out—as in this case—that stratigraphy isn’t uniform. When researchers excavated elsewhere in the Liang Bua cave, they found new stratigraphic details (erosion of older deposits followed by filling in of younger deposits) that prompted them to redate the sequence. These new data gave a range of 100-60,000 YBP for the skeletal remains of H. floresiensis and 190,000-50,000 for floresiensis-associated artifacts. The end of this date range—50,000 YBP—happens to be close to the estimated appearance time of modern H. sapiens on the island, which raises some intriguing questions. For those of you interested in a detailed analysis of the errors of the original dates, and a discussion of some still-unresolved issues with the paper, I highly recommend John Hawks’ post What the revised Liang Bua chronology leaves unanswered.

Unfortunately, some in the media have gone beyond discussion of those questions and breathlesslyreported that these new dates likely mean that our species wiped out the hobbits. While that hypothesis certainly remains a formal–and fascinating– possibility, it’s only one of several. It’s based simply on the observation that under the current chronology, approximately the same time modern humans got to Flores, we stop seeing hobbit tools in the deposits at Liang Bua.

But I want to point out that we have no direct evidence (as yet) showing any interaction between H. sapiens and H. floresiensis, as the authors noted in the closing sentence of their manuscript:

“Parts of southeast Asia may have been inhabited by Denisovans or other hominins during this period, and modern humans had reached Australia by 50 kyr ago. But whether H. floresiensis survived after this time, or encountered modern humans, Denisovans or other hominin species on Flores or elsewhere, remain open questions that future discoveries may help to answer.”

So as of right now, we actually don’t know that humans killed off (either directly or indirectly) hobbits. But this is probably the interpretation that the interested public has walked away with after this week. Call me conservative, but I’m a bit uncomfortable that our speculation might have given people the impression of greater certainty than we actually have.

There are two other aspects of this new finding that interest me. The first is the implication that these older dates have for the debate over whether H. floresiensis was a pathological modern H. sapiens or a separate species with distinctive morphology, likely caused by insular dwarfism. The older date range for these fossils suggests that H. floresiensis was indeed a separate species. Furthermore, as Kristina Kilgrove discusses, these new dates also undermine cryptozoological interpretations of the Indonesian legend of Ebu Gogo as deriving from sustained interactions between humans and H. floresiensis as recently as 12,000 years ago.

The second aspect of these new dates that I find interesting is that although they mean that the hobbits were older than we initially thought, they still fall within the range of time in which it’s possible to obtain ancient DNA from skeletal remains. I have no idea whether there will be further attempts to extract aDNA from the hobbits (previous attempts were unsuccessful), but I continue to be hopeful that someday we will have hobbit DNA. If H. floresiensis is, as some suspect, a descendant of H. erectus, then their genomes could give us a glimpse of that species’ genetic diversity and help us better understand the evolutionary history of ourselves, Neanderthals, and Denisovans.

Story after story about sexual harassment of students and trainees by professors has been coming out recently. Today Michael Balter has just published an important news piece about the same thing happening much closer to home–in my discipline, physical anthropology. Specifically, in the subfield of paleoanthropology.

The story is very complex, but the gist is that a young research assistant has come forward with allegations that she was sexually assaulted by her supervisor, Brian Richmond, in his hotel room at a European conference.

Outsiders may never know for sure what happened in that Florence hotel room. But the incident ultimately triggered a cascade of other allegations against Richmond and a resolve by some senior paleoanthropologists to do battle against sexual misconduct, hoping to change the climate of their field. The charges and the community’s response also roiled two leading institutions, which struggled with shifting cultural expectations, inadequate reporting and disciplinary tools, and the challenge of treating all parties fairly.

Colin is currently on the ConspiraSea Cruise doing research for a book on irrational beliefs. He is emailing summaries of each day’s experiences to me for posting here on Violent Metaphors. This is the fourth day’s report. You can read Day 1 here, Day 2 here , Day 3 here, day 5 (part 1) here, day 5 (part 2) here , and an explanation for what he is doing here. If you would like to give him questions or advice, please comment on this post–I’ll make sure he sees it. –Jennifer

When I started this project, many (many many) people warned me to be careful and that I might be in danger. I didn’t take that possibility seriously then, and I don’t take it seriously now—I personally have never felt unsafe at this conference. But I am not the only writer here. And the others, who unlike me are professional journalists, will tell their stories eventually. Until then I’d like to share the events of the last couple of days. This is a story about a long series events taking place at a confusing and busy event; it’s going to be long and busy and confusing at times. Sorry. (Note: Colin emailed me two days’ worth of material in a single batch, and I split them up by day to make this post more manageable. You can read part 2 here.–Jennifer). You want clear and concise and comprehensible stories, read about a conference that doesn’t feature an antivaccine guru, a pistol-packing presidential candidate, a self-employed and self-declared “international judge” and an alchemist all on the same boat. What I’ve got is what they gave me. Continue reading →

Colin is currently on the ConspiraSea Cruise doing research for a book on irrational beliefs. He is emailing summaries of each day’s experiences to me for posting here on Violent Metaphors. This is the third day’s report. You can find the first day’s report here, the second day’s report here, the fourth day’s report here, the fifth day’s report (part 1) here, day 5 (part 2) here , and an explanation for what he is doing here. If you would like to give him questions or advice, please comment on this post–I’ll make sure he sees it. –Jennifer

Today’s post will be relatively short, for a few reasons. Primarily it’s because even though I’m on a cruise ship, this is exhausting! Everything starts around 8 am and ends around 10 pm. The ship is full of amenities—bars, restaurants, minigolf, swimming pools, hot tubs, saunas, a library, coffee shops, massages, shopping, comedy shows, movie theaters, and god know what else. I don’t, because I haven’t used any of those things except a couple of restaurants, a coffee shop, and the treadmill. I’m not complaining, though, because the important stuff is here. I’m meeting fascinating people, and that’s not a euphemism. For the most part, the people here are pleasant and engaging and well worth getting to know. Continue reading →

Colin is currently on the ConspiraSea Cruise doing research for a book on irrational beliefs. He is emailing summaries of each day’s experiences to me for posting here on Violent Metaphors. This is the second day’s report. You can find the first day’s report here, day 3 here, day 4 here, day 5 (part 1) here, day 5 (part 2) here and an explanation for what he is doing here. If you would like to give him questions or advice, please comment on this post–I’ll make sure he sees it. –Jennifer

This is Jennifer’s blog, and Jennifer is a scientist. So most of the posts here are about science in one way or another. And I love that, because I love science—the idea of it, the practice of it, and the success of it. So when we talk about irrationality and pseudoscience, it’s only natural that we’re mostly focused on pseudoarchaeology, pseudogenetics, anti-vaccine and anti-GMO irrationality. There’s plenty of that on this boat and I’m going to write about it, but so far it’s nothing new.

This post isn’t about pseudoscience. Not about anti-vaxers or GMO fearmongering. Lots of our readers come here for those topics, but don’t turn away just yet. I want to talk about something most of you have barely thought about, but something that may be more important than anti-vaccine pseudoscience—at least for its victims.

As much as I love science, I’m not a scientist. I’m a lawyer. I graduated from Harvard Law School, served as a staff clerk for the Seventh Circuit Court of Appeals, and clerked for a very respected federal judge in Texas. Before I left the practice I spent years litigating cases for an international law firm, doing things like suing a hedge fund for committing fraud in the securitization of esoteric financial instruments. I don’t say any of this stuff to put on airs. It never once got me a date when I was single. I just want to establish that while I’m not a famous legal scholar or law school professor or distinguished expert, I know more than a little something about how courts and laws work. That’s why this post isn’t about pseudoscience but pseudolaw.

And it matters. Pseudolaw isn’t harmless. It ruins lives. It sends people to prison. People die behind this, as you’ve seen happen in Oregon. The pseudolaw that’s happening on the boat is tame by comparison, but still has the potential to wreck the lives of well-meaning people. It’s important to take a break from pseudoscience to see how this slow-motion disaster is happening in front of our eyes, and then we’ll take a look at how it’s affecting the anti-vaccine movement.

This is a harsher post than I expected to write, and much harsher than I’ll be writing about the rest of the cruise. If you’re on the cruise with me and reading this, please do it with an open mind. This is what it means to seek the truth, which is what the cruise is supposed to be helping us all do. Continue reading →

Edit: A reader informed me that the first source I cited (christwire.org) was actually a satirical site. How embarrassing! I’ve since updated the post with a legitimate example. Fortunately (or unfortunately, depending on how one looks at things) it took me approximately 5 seconds to find it.

There’s a persistent belief in creationist circles that the theory of evolution is a house of cards that will collapse if an astute, open-minded person just looks at it hard enough. To facilitate this process, creationists pass around lists of questions which they are certain evolutionists “can’t answer.” The questions emphasized vary from group to group, but the suggested tactic is the same: publicly confront an evolutionist, ideally a professor or teacher, and confound him or her with questions that will expose the structural weaknesses of the theory. From Creation Today:

NOTE TO STUDENTS: Make a copy of this challenge to evolutionists and ask your teacher or professor to give you answers to these questions. If they cannot, you have a right to be skeptical that what they are teaching about evolution is true. Also, give copies to your fellow students so that they, too, will be aware that there are huge flaws in the theory of evolution. It is still a theory, not a “fact.

The questions from the source above include things like:

What are the odds that the evolutionary process, proceeding by random changes, would produce human beings, plus millions of species of animals, birds, fish and insects, all with symmetrical features, i.e., one side being a mirror image of the other? We take symmetry in all these creatures for granted, but is that a reasonable outcome for a random process?

Where are the trillions of fossils of such true transitional forms?

What are the odds that, of the millions of species of animals, birds, fish and insects, a male of each species developed at the same time and in the same place as a female of the same species, so that the species could propagate? Why are there two sexes anyhow?

Of course, anyone who has taken a high school introductory biology course should be able to answer questions like these (or point out exactly how they are flawed.) I say “should be able”, but unfortunately that is not always the case. This semester I taught an introductory university course in physical anthropology* in which we intensively studied human evolution, beginning with basic concepts in genetics and evolutionary theory and finishing with an overview of the hominin fossil record. (I used Clark Spencer Larsen’s “Our Origins” as the textbook). I discovered early in the semester that about half the class was not well prepared for this material: many knew absolutely nothing about human evolution, and a sizable number knew very little about evolution in general. It’s not the students’ fault. Science education in Kansas (where I teach) has been under attack for some time by a coalition of religious groups trying to prevent the teaching of evolution in public high schools, and I suspect that my students’ lack of preparation might be at least partially attributable to this. But that’s a subject of another, longer post in the future.

Regardless of how little they know coming in to the course, I want my students to walk out of the classroom with a solid knowledge of how evolution works. In five years’ time, they may have forgotten the morphological differences between the teeth of Australopithecus afarensis and Homo erectus , or the phylogenetic relationships of Denisovans to Neandertals and H. sapiens as inferred from ancient genomes (although I hope they don’t!), but if they have a basic understanding of how evolution works as a process, they should be able to understand the significance of new fossil or genetic discoveries. Similarly, if they understand the difference between science and pseudoscience, they should be able to evaluate factual claims. The difficulty for me was figuring out how to present these ideas when the course is already jam-packed with information the students needed to learn in order to advance.

So I tried something new. One of the questions that some creationists (and people who simply don’t know a lot about evolution) frequently ask to challenge evolution is: “If we evolved from monkeys, why are there still monkeys?” (I see this question asked every single day on Twitter, thanks to the account of @TakeThatDarwin who retweets creationists). In the past I’ve simply rolled my eyes at how ridiculous the question is–in fact, several groups like Answers in Genesis, strongly urge their readership not to use it–but I recently realized that it nicely gets at some very serious and common misunderstandings about evolution. I decided to experiment with using it to further students’ critical thinking.

I gave this question to students to answer several times throughout the course. First, I used it as a means of (anonymously) assessing their knowledge about evolution as a process early in the course. About a fourth of the class gave confused answers to it, and another fourth could answer it partially but without sufficient detail. After we had gone through basic concepts of evolutionary theory, genetics, and primate phylogenies (but before we got into the hominin fossil record), I made it the subject of an in-class discussion, so students could learn from each other’s answers. At that point, they had the basic tools to answer the question, and those who participated in the discussion were able to answer it in some detail. Finally, as a means of reinforcing students’ knowledge at the end of the course, I gave it as the last extra credit question on the final exam. Nearly everyone who chose to answer this question received full credit.

I was looking for two parts in their response: 1. A recognition that we did not evolve from monkeys–or other living primates– but instead share a common primate ancestor. (Bonus points for recognizing that the category ‘monkey’ is paraphyletic and is a colloquial term, not a scientific taxon). 2. An understanding that evolution doesn’t work in a linear fashion, with one species replacing the last. There are many good analogies to use in teaching this concept; I like to use the analogy of a family tree: that is, I and my sister are both descended from the same parents, yet we exist at the same time.

My sister and I came from the same parents, but we’re both able to exist at the same time. Here’s evidence of us existing while we talk about evolution with our friends Joe Silva and Sean Shelby.

This approach allowed the class to confront some of the major misconceptions of evolution, including the idea that modern animals transform into other kinds of modern animals, that there is a predetermined “order” to evolution, and that evolution is a “finished” process. It served as a platform to discuss several important concepts: adaptations, natural selection, heredity, and that evolution occurs in populations, not individuals. I saw a distinct progression in students’ reasoning on this question over the course of the semester, and I think that it proved to be pretty useful in the end.
Another approach I used to supplement the textbook (because the findings were so new they weren’t in the textbook) was to show students two video clips offering two very different perspectives on the newest hominin fossil, Homo naledi. The first was by Kent Hovind (I started at 9 minutes in, and we watched for about 10 minutes or so).

The second was by National Geographic, and included clips from paleoanthropologist Lee Berger who discovered H. naledi.

I asked students to identify two or three testable claims presented in each video, and think about what kinds of evidence would be needed to test these claims. This sparked a very lively and (I think) helpful discussion in class which covered radiometric dating methods and their limitations, how to interpret clues about behavior from the fossil record, and a brief discussion on how fossil discoveries are portrayed in the media. We ended by discussing how new information about human ancestors–derived from fossils, archaeology, and genetics– is evaluated by the scientific community.

While I’m on break, in addition to catching up on all the writing I didn’t have time for during the semester (how do people stay on top of all of this?), I’m looking for more materials that would be good for these kinds of exercises in critical thinking. I just found the Institute for Creation Research’s document summarizing the “scientific” case against evolution, and I think that there are some very useful instances of misconceptions that could work well as the basis for student research and discussion. For example, the following statement could serve as a useful starting point for students to think critically about taxonomy, evo-devo, and both early and later primate fossil records:

Fossil discoveries can muddle over attempts to construct simple evolutionary trees — fossils from key periods are often not intermediates, but rather hodge podges of defining features of many different groups. . . . Generally, it seems that major groups are not assembled in a simple linear or progressive manner — new features are often “cut and pasted” on different groups at different times.11

As far as ape/human intermediates are concerned, the same is true, although anthropologists have been eagerly searching for them for many years. Many have been proposed, but each has been rejected in turn.

But I’d like to find more. To any professors who teach evolution who read this blog, I want to ask: In addition to assigned readings, traditional lectures, and labs, what approaches do you use for teaching on the fundamentals of human evolution (or evolutionary theory)? Do you do something similar?

To anyone else who reads this blog, I want to ask: How did you first learn about evolution, and human evolution in particular? Have you ever changed your mind on the subject? If so, what caused you to change your mind?

————————————————————————————————–

*Regular readers of my blog may have noticed a precipitous drop in the frequency of postings over the last few months. This is why.

Just a few days ago, my co-author Deborah Bolnick and I published a paper in the journal PaleoAmerica on the subject of haplogroup X and Native American population history. Rather than writing a blog summary of it (which has been my usual approach for publications), we decided to try something different: make the paper itself open access and respond here to a few questions about it that we’ve seen from a variety of sources. We hope that this approach will be helpful to interested readers!

What is the paper about?

We reviewed existing genetic data to answer the question: Could mitochondrial haplogroup X2a have been brought to the Americas by an ancient trans-Atlantic migration? This is a rather old question from the perspective of anthropological geneticists, but we’ve seen it appear in both academic publications and documentaries rather frequently. We thought it was worth revisiting in light of recent genetic publications.

Quite simply, we found that mitochondrial and genomic data do not support this migration hypothesis as the most plausible explanation for X2a’s presence in North America. Instead, the most parsimonious interpretation of the genetic data continues to be that haplogroup X2a had the same migration history and ancestry as the other founder Native American mitochondrial lineages (i.e., from Siberia). Based on the current evidence, we feel that there is no need to invoke a distinct origin for individuals bearing this lineage.

If’ you’d like another summary of the paper, Andy White wrote a very good blog post about it here.

Where can I get a copy?

We’ve sent a request to the publisher to make the paper open-access, and are waiting for them to process the request. We’ll update this post with a link as soon as the process is finalized. In the meantime, you can email us for a copy or find it on Jennifer Raff’s academia.edu page

How can you say that this proves once and for all that all Native Americans have exclusively Beringian ancestry when you haven’t sequenced all of them? Isn’t that unscientific?

We don’t say that. This work presents our best interpretation of all the genetic evidence currently available that are relevant to this question. In fact, we end the paper saying:

It is of course possible that genetic evidence of an ancient trans-Atlantic migration event simply has not been found yet. Should credible evidence of direct gene flow from an ancient Solutrean (or Middle Eastern) population be found within ancient Native American genomes, it would require the field to reassess the “Beringian only” model of prehistoric Native American migration. However, no such evidence has been found, and the Beringian migration model remains the best interpretation of the genetic, archaeological, and paleoclimate data to date.

We don’t think it’s likely that new evidence will suddenly crop up showing another source of ancestry for Native Americans, but it remains a formal, albeit remote, possibility. Should such evidence be found, it will require us to reexamine our models. But we can’t incorporate hypothetical results into our interpretations. That would be unscientific.

Doesn’t skeletal data contradict the Beringian hypothesis? What about the very early Paleoindians whose skulls look physically different from later and contemporary Native Americans? Aren’t they proof that Native Americans have European ancestry?

The skeletal data show changes over time in the cranial morphology of ancient Native American populations. It’s true that comparisons of skull shapes were, for a very long time, how anthropologists studied genetic relationships between populations. However, over the last few decades, we’ve developed the technology to assess biological relationships between individuals and populations by comparing genomes. It’s generally acknowledged that this is a more precise, direct means of assessing ancestry than morphology, which can be influenced by environmental, developmental, and cultural factors.

Furthermore, the genomes of several of the Paleoindians with differently shaped crania have been examined, and they show no evidence of different ancestry than later or contemporary Native Americans. For example, Kennewick Man, who we discuss in the paper, exhibited what some have described as “Caucasoid” cranial features. However, his overall genetic affinities group him with Siberians/East Asians, not Europeans. And his mitochondrial haplogroup is the most basal lineage of X2a so far observed. This result shows that X2a—and this Paleoindian cranial morphology—are compatible with Siberian ancestry.

Why the skulls of the earliest inhabitants of the Americas look different from the later indigenous inhabitants is a very interesting question. We suspect it has to do with evolutionary forces like selection or drift acting on morphology over millennia. Current genomic research just doesn’t show evidence that they had different ancestry from later Native American groups.

Isn’t it pretty well proven that Clovis technologies are descended from Solutrean technologies?

No. The majority of archaeologists think that the similarities between the Clovis and Solutrean points are either spurious or coincidental. Very, very few archaeologists interpret the data as supporting the Solutrean hypothesis. We don’t see the genetic evidence as supporting the Solutrean hypothesis either.

Archaeologists were wrong about the “Clovis First” hypothesis, so doesn’t that mean that you’re wrong too?

Why? These are two separate models. The model of Beringian genetic ancestry of Native Americans is not dependent on the Clovis First hypothesis; in fact, the same evidence from which the “Beringian Pause” model was developed—early coalescence dates of mitochondrial lineages and ancient DNA data—was an important component in overturning the Clovis First model.

In science, any hypothesis is falsifiable, and any model is provisional pending contradictory data. The overturning of the Clovis First model is a great example of the process working as it should.

Isn’t it unfair to critique the Solutrean hypothesis before it’s been fully “fleshed out?” There’s bound to be more data supporting it soon!

Any hypothesis is open to testing, otherwise it’s not scientific. And there’s no “waiting period” to protect a hypothesis until it’s gathered enough data to make it immune to criticism. This argument is a species of special pleading—no other idea in archaeology is treated this way.

What about the signal of “West Eurasian” ancestry seen in Native American genomes? Does it support a trans-Atlantic migration?

This finding has led to a lot of confusion among non-geneticists, and we address it in some detail in the paper. To summarize: Raghavan et al. (2014) and Rasmussen et al. (2014) studied the genomes of the Siberian Mal’ta individual and the Anzick-1 individual, respectively, and they found that a portion of their ancestry (between 14-38%) was derived from a population that also contributed alleles to the contemporary inhabitants of West Eurasia. Notably, the contemporary European gene pool appears to have emerged quite recently—within the last 8,000 years—as a result of significant migration and admixture events. We don’t know what the genomes of Solutrean peoples looked like, since none have been sequenced yet, but from these findings we predict that they would more closely resemble pre-Neolithic hunter-gatherers than contemporary Europeans [see Allentoft et al. 2015, Haak et al. 2015, and Lazaridis et al. 2014]. Importantly, based on the pre-Neolithic genomes that have been studied, it appears that these early European hunter-gatherers did not exhibit close genetic affinities to Native Americans.

Several studies have also formally tested the evolutionary relationships between Native American genomes and genomes from ancient and contemporary populations worldwide (see Rasmussen et al. 2015, Raghavan et al. 2015, and Lazardis et al. 2014). These studies have consistently showed that the model which best fits the current genetic data did not match the predictions of the Solutrean hypothesis. We discussed this in the paper, noting that the most supported model:

was one in which the population ancestral to Native Americans was derived from ancient North Eurasian and East Asian sources, while contemporary Europeans were derived from ancient North Eurasian and West Eurasian sources. In other words, gene flow was from the ancestral North Eurasian population into both the ancestral Native American and ancestral European populations. Lazaridis et al. (2014) did not find any evidence of Pleistocene gene flow directly from West Eurasians into Native Americans. Their model is also consistent with other studies, which have shown that 62-86% of Native American ancestry derives from East Asia.

We’ll update this FAQ with the answers to more questions as they arise, so do check back. If you have any questions, feel free to leave them in the comments section and we’ll try to get to them as soon as our schedules allow.